Ultrasound elastography of back muscle biomechanical properties: a systematic review and meta-analysis of current methods

Objectives To report the current elastography methods used to quantify back muscles’ biomechanical characteristics in patients with musculoskeletal disorders (MSKd) and inform on their reliability, validity, and responsiveness. Methods MEDLINE, Embase, CINAHL, Cochrane library and grey literature were consulted. Predefined criteria allowed for study selection and data extraction. The quality of evidence was rated using the COSMIN tool. Data were meta-analyzed in terms of pooled intraclass correlation coefficient (pICC) for reliability and pooled standardized mean difference (pSMD) for validity and responsiveness. Heterogeneity was assessed. Results Seventy-nine studies were included in the meta-analysis (total number of participants N = 3178). Three elastography methods were identified: strain imaging (SI; number of cohorts M = 26), shear wave imaging (SWI; M = 50), and vibration sonoelastography (VSE; M = 3). Strain imaging and SWI studies reported good reliability measurement properties (pICC > 0.70) and a medium pSMD (0.58 for SI and 0.60 for SWI; p ≤ 0.020) in discriminating MSKd from controls’ condition (validity). Strain imaging studies reported a medium pSMD (0.64; p = 0.005) in detecting within-group changes over time, whereas SWI pSMD was very high (1.24; p = 0.005). Only SWI reported significant but small pSMD (0.30; p = 0.003) in detecting between-group changes over time. The small number of VSE studies could not be meta-analyzed. Heterogeneity was high (I-squared > 90%; p < 0.001). Conclusions Elastography presents good reliability results and a medium pSMD in discriminating MSKd from control conditions. Responsiveness data suggest detectable changes within groups over time using SI and SWI, calling for long-term longitudinal studies. Assessing changes between groups over time using elastography still needs to be proven. Highly significant heterogeneity limits meta-analytic results. Critical relevance statement While still in its early-stage exploration phase, musculoskeletal ultrasound elastography may reliably quantify back muscles’ biomechanics in asymptomatic individuals, moderately discriminate back musculoskeletal disorders and detect biomechanical changes over time in these conditions, calling for long-term longitudinal studies. Key Points Ultrasound elastography is reviewed for back pain and related musculoskeletal disorder assessments. Growing literature supports good reproducibility, some validity and responsiveness. Back muscle elastography considers assumptions calling for standardized protocols. Graphical Abstract

Rest lying on its side.In the upper trapezius approximately midway between the cervical vertebrae and the acromion process:

Strain imaging Manual compression
(1) A-MTPs that changed from active to latent or palpably normal tissue after treatment (defined as "responded").
(2) A-MTPs that changed from active to palpably normal tissue after treatment (defined as "resolved").(3) A-MTPs that responded but did not resolve ("active to latent").Tau-squared: variance of the standardized mean difference across studies; I-squared: proportion of total variance between studies that is attributed to heterogeneity; Q: heterogeneity statistic; M: number of cohorts; N: number of participants; df: degree of freedom; F-squared: F statistic of the meta-regression.Sig.: P value associated with the F statistic; R 2 : proportion of total variance that is explained by the variable under interest.
Tau-squared: variance of the standardized mean difference across studies; I-squared: proportion of total variance between studies that is attributed to heterogeneity; Q: heterogeneity statistic; M: number of cohorts; N: number of participants; df: degree of freedom; F-squared: F statistic of the metaregression Sig.: P value associated with the F statistic; R 2 : proportion of total variance that is explained by the ultrasound excitation method used.

Table S1 -
Medline strategy.Ovid MEDLINE(R) ALL 1946 to February 15, 2023 * or cat or cats or dog or dogs or feline or hamster* or lamb or lambs or mice or monkey or monkeys or mouse or murine or pig or pigs or piglet* or porcine or primate* or rabbit* or rats or rat or rodent* or sheep* or veterinar*) not (human* or patient* or women or men)).ti,kf,jw.

Hartung method is used for standard error adjustment. b. Some statistics cannot be computed because this subgroup contains a single record
. pSMD: pooled standardized mean difference; ID: study identification; SE: standard error of the pooled effect size.CI: confidence interval; t: t statistic of the pooled effect size; Sig.: P value associated to the t statistic.